Amides are versatile and important synthetic intermediates used in the production of a variety of plastics, detergents, lubricants, and polymers. Traditional methods of hydrating nitriles to amides involve the use of strong bases or acids, enzymes, or heterogenous catalysts, but these traditional methods suffer from various drawbacks.
For example, strong acids or bases are generally used in stoichiometric excess (e.g., 96% H2SO4 or 50% KOH/t-BuOH) under harsh conditions, which often induces further hydrolysis of the desired amides to carboxylic acids thereby lowering the yield thereof. Moreover, poor tolerance for other functional groups is often observed under such harsh acidic or basic conditions. While performed under much milder conditions, enzymes are often sensitive to the variation in structure of the nitriles and the reaction conditions. Moreover, slow reaction rates, low conversions, and reproducibility are common problems encountered with enzymatic reactions. Heterogeneous catalysts, such as zeolites and metal oxides, often produce poor yields and demonstrate poor tolerance for other functional groups.
Transition metal complexes offer a potential alternative to the traditional approaches. A variety of transition metal complexes have been developed as catalysts for nitrile hydration in organic media, but many of these transition metal complexes are often air-sensitive and/or non-recyclable catalysts.
Accordingly, new catalytic methods or processes for the conversion of nitriles to amides that overcome one or more of the deficiencies of the traditional approaches are needed.